A case of a radiation-induced osteochondroma occurring in the posterior elements of the L3 vertebra in a 29-year-old woman is reported. At age 16 months, the patient was treated for an abdominal neuroblastoma. There were also radiation changes affecting the spine, ribs, and ilium. The lesion was excised "en bloc" and a spinal fusion performed. This is the third reported case of such a lesion occurring in the lumbar spine consequent to radiation therapy. The extremely long, latent period between radiation treatment and diagnosis of secondary tumor should be noted.